Fire plays a vital role in forest ecosystems. At low intensity, wildfires can kill insects and diseases that harm trees, clear away underbrush and debris to provide more space for grasses, herbs, and shrubs, and open up sunlight to nourish young plants. Scientists who study wildfire include fire ecologists, fire engineers, climate scientists, and social scientists.
Wildfires are unpredictable and can occur anywhere in the world where there is vegetation and weather conditions that can support it. Over the past century, many areas of the United States have experienced wildfires more frequently and at higher intensity than in the past due to changing climate, human activity, and decreased forest management efforts.
The majority of wildfires are started by humans. Ignitions from fireworks, faulty power lines, runaway campfires, and chainsaws are common causes of fire. Other ignitions may be the result of wildland encroachment by invasive species like eucalyptus in California, gamba grass in Australia, and some conifers in Europe.
Prescribed burns can help decrease the amount of combustible fuels in an area, and can promote healthy fire-adapted ecosystems. However, the number of homes located in areas with high wildfire risk has grown rapidly, especially in the US, increasing the potential for damage by a large and uncontrollable wildfire. Moreover, air pollutants from burning wildlands, such as PM2.5 (particulate matter 2.5 microns or smaller in size), can increase the risk of cancer in people.